The high volume demanded by the pharmaceutical market has placed great pressures upon the manufacturing arts related to making tablets and dispensing them into containers. For purposes herein, the term "tablet" will refer to any of the numerous compressed tablet, gelatin capsule or other solid dose forms of oral drugs, both prescription and non-prescription, as well as analgesics, vitamins and other products dispensed in tablet or capsule form. After a quantity of tablets has been manufactured, they are usually stored or shipped in a bulk container. The present invention relates to methods and apparatus for transferring tablets from bulk into smaller containers such as bottles. Typically, these containers will be those provided directly to the end user, however, in some instances the container or bottle will be for intermediate storage, e.g., for use in a hospital or pharmacy.
Individual bottles may be filled with tablets using a device known as a continuous slat counter. Such devices typically comprise a moving bed made up of a series of grooved slats which passes beneath a quantity of tablets. The grooves are further subdivided into cavities and one tablet is permitted to drop into each cavity until all the cavities are filled. After the filled slats move from beneath the stationary quantity of tablets they are inverted, the tablets fall out and are collated and fed into each bottle via transport through a manifold system.
For example, U.S. Pat. Nos. 3,139,713; 4,185,734; 4,241,293; and 4,680,464, all of which are assigned to Pennwalt Corporation of Philadelphia, Pa., disclose an article counting machine for filling bottles that uses a stationary quantity of tablets disposed above a moving bed of slats. These patents recognize that these machines can miscount articles when a tablet is wedged in a cavity or when a cavity is empty. In this regard, U.S. Pat. No. 4,241,293 discloses an ejector blade that protrudes from the base of the cavity and ejects tablets wedged in the cavity. U.S. Pat. Nos. 4,185,734 and 4,680,464 both disclose optical scanners for detecting the presence or absence of a tablet from a particular cavity.
Another version of a continuous slat article counting and filling machine is disclosed in U.S. Pat. No. 3,925,960, assigned to the Lasko Company of Fitchburg, Mass. In this system, the slats and cavities are oriented horizontally, i.e., coaxial with the axis around which they are moving. A series of chutes collects the counted tablets and delivers them to a moving series of containers. Another, more recent variation of slat counting machines is disclosed in U.S. Pat. No. 4,674,259, assigned to Package Machinery Co. of Longmeadow, Mass. This machine uses vertically-oriented set of slats with cavities that deliver the counted product to a series of chutes that shuttle alternately between a first and a second row of containers.
In all of the above-described continuous slat counter bottle filling systems, the tablets are directed into the cavities in the slat by the force of gravity. However, mechanical vibrations have been imparted to the slats and to the stationary quantity of tablets over the continuously moving bed of slats to assist the tablets in falling into the cavities.
In any event, if the slats are positioned beneath the stationary quantity of tablets for a sufficiently long period of time, every cavity will eventually be filled. However, since the slats are continuously moving beneath the quantity of product, the amount of time a given slat spends beneath the product will be directly related to the speed of the slats' movement. Therefore, if the speed of the slats is increased, the time beneath the quantity of product may not be sufficient to ensure that all the cavities are filled. As a result, a severe limitation within most slat counter bottle filling systems in that the speed at which the slats move beneath the quantity of tablets cannot exceed a certain level. If the speed is increased above this level the number of empty cavities quickly rises, resulting in underfilled bottles.
The probability of tablets filling the slat cavities also depends upon the shape of the tablet. The easiest tablet to handle would be a spherically shaped tablet. As a tablet's dimensions change to become thinner or longer or irregularly shaped, the time required for a tablet to fill the empty cavities increases. With irregularly shaped tablets, it may take such a long time to fill the cavities that the operating speeds of state of the art tablet bottle fillers will be extremely slow. To solve this problem, one method the state of the art filler manufacturers use is to enlarge the cavities to allow the tablets to fall into the cavities quicker. The drawback to this approach is that as the cavities become oversized, the frequency of wedging and getting two tablets within one cavity will become a problem.
It would therefore be desirable to be able to increase the speed at which slat counter bottle filling machines operate. It is further desirable to ensure that every cavity of a slat is filled with a tablet. Accordingly, it is an object of the present invention to increase the speed of a slat counter bottle filler without sacrificing filling and counting accuracy.